DESCRIPTION: In the mammalian olfactory system, a topographic map of receptor activation defines the quality of an olfactory sensory stimulus. Neurons expressing a given receptor, and therefore responsive to a given odorant, project with precision to two of the 1800 topographically-fixed glomeruli within the mouse olfactory bulb. Since the position of individual glomeruli are topographically defined, the bulb provides a spatial map that identifies which of the numerous receptors have been activated within the sensory epithelium. The identification of an invariant topographic map of odor quality immediately poses the interesting question as how this map is established during development and how it changes with experience. This project focuses on the role of activity-dependent plasticity in the establishment, maintenance, and refinement of a topographic map of olfactory sensory projections.